Network computer systems generally include a plurality of geographically separated or distributed computer nodes that are configured to communicate with each other via, and are interconnected by, one or more network communications media. One conventional type of network computer system includes a network data storage subsystem that is configured to provide a centralized location in the network at which to store, and from which to retrieve data. Advantageously, by using such a storage subsystem in the network, many of the network's data storage management and control functions may be centralized at the subsystem, instead of being distributed among the network nodes.
One type of conventional network data storage subsystem, manufactured and sold by the Assignee of the subject application (hereinafter “Assignee”) under the tradename Symmetrix™ (hereinafter “the Assignee's conventional storage system”), includes a plurality of disk mass storage devices configured as one or more redundant arrays of independent (or inexpensive) disks (RAID). The disk devices are controlled by disk I/O controllers (commonly referred to as “back end” directors) that are coupled to a shared cache memory resource in the subsystem. The cache memory resource is also coupled to a plurality of host I/O controllers (commonly referred to as “front end” directors). The disk controllers are coupled to respective disk adapters that, among other things, interface the disk controllers to bus systems (e.g., small computer system interface (SCSI) based bus systems) used to couple the disk devices to the disk controllers. Similarly, the host controllers are coupled to respective host channel/network adapters that, among other things, interface the host controllers via channel input/output (I/O) ports to the network communications channels (e.g., Gigabit Ethernet, SCSI, Enterprise Systems Connection (ESCON), or Fibre Channel (FC) based communications channels) that couple the storage subsystem to computer nodes in the computer network external to the subsystem (commonly termed “host” computer nodes or “hosts”).
In one conventional data storage network arrangement, a standalone network switch may be interjected in the communications channels intermediate to the host adapter I/O ports and the host nodes. More specifically, the host adapter channel I/O ports may be coupled to a first set of the switch's I/O ports, and a second set of the switch's I/O ports may be coupled to the host nodes. In this conventional data storage network arrangement, if the standalone network switch is appropriately configured, the host adapters (and their associated host controllers) may be able to exchange data/commands via the switch with any of the host nodes.
Unfortunately, standalone network switches tend to be relatively expensive and complex devices that may require substantial amounts of time and effort to install, configure, manage, and maintain in the data storage network. Also unfortunately, the presence of a standalone switch in the data storage network introduces into the network another stage, or hop, that the data must pass through when the data moves from the host nodes to the data storage system, and vice versa; this may increase latency in moving data from the host nodes to the data storage system, and vice versa.